This invention relates generally to orthopedic devices for the feet, and relates more specifically to an improved foot stabilization apparatus for controlling gait by limiting excessive pronation and assisting in resupination of the foot during walking or running. A related apparatus and method is disclosed in U.S. Pat. No. 4,392,487 issued to Applicants.
A normal human gait cycle consists of three phases: the contact phase in which the heel alone initially makes contact with the ground, the mid-stance phase in which the entire sole or plantar surface of the foot is in contact with the ground, and the propulsive phase wherein the balls of the foot and the toes push off. During the gait cycle, the foot and ankle tend naturally first to undergo movement known as pronation and then to move in a manner known as supination. While these movements of the foot and ankle are complex and can only be accurately described with reference to the three conventional anatomical planes (i.e., the sagittal, frontal and transverse planes), in simple terms pronation is an inward rolling and supination is an outward rolling of the foot and ankle.
More specifically, pronation and supination of the foot and ankle are a function primarily of the subtalar joint and the midtarsal joints. The subtalar joint is defined as the articulation between the talus and calcaneus (heel) bones. The midtarsal joints comprise the calcaneal-cuboid joint, which is defined as the articulation of the calcaneus and cuboid bones, and the talar-navicular joint, which is defined as the articulation of the talus (ankle) and the navicular bones. The navicular bone forms part of the arch structure.
A certain amount of pronation of the foot during walking or running is desirable. Generally speaking, pronation occurs during the contact phase and about the first half of the mid-stance phase of a normal gait cycle. In the pronated position, the bones of the foot tend to become mobile or loose relative to one another, allowing the plantar surface to adapt to possibly uneven terrain. During the last half of the mid-stance phase and during the propulsive phase, however, resupination is essential so that the bones of the foot become relatively stable or locked to enable one to push-off.
Although some pronation is normal, many persons are troubled by excessive pronation in which the foot and ankle roll too far inwardly and the bones of the foot become hypermobile relative to one another. The combination of excessive pronation and resupination during a gait cycle can result in exaggerated back and forth rotational movement of the leg and knee with accompanying results that are highly undesirable. For example, various forms of muscular fatigue in children (sometimes called "growing pains") and in adults (such as back pain and leg fatigue) have been traced to excessive pronation. Likewise, excessive pronation has been found to be a cause of arch strain, heel pain, pain in the knee joint and the patella (knee cap), and foot deformities such as bunions and hammer toes (which in turn can result in corns and calluses). The effects of excessive pronation are particularly a problem for athletes, including those who run or jog.
Various attempts have been made by the prior art to lessen or eliminate the effects of excessive pronation. The most commonly attempted solution has been use of conventional arch support wedges. This approach is believed motivated by the fact that pronation is accompanied by a general stretching and flattening of the arch, and persons with flattened arches tend to suffer more frequently from the effects of excessive pronation. However, use of arch support wedges has been found to be a generally ineffective solution that is directed to a symptom rather than the source of the problem. Some persons have flattened arches and do not excessively pronate, while other persons with raised arches suffer greatly from the effects of excessive pronation. Excessive pronation does not result from flattened arches, but rather is primarily the result of the internal structure of the foot and ankle, and in particular the motions of the subtalar and midtarsal joints. It is also influenced by external forces generated by knock-kneed, pigeon-toed or duck walking, for instance. Arch support wedges cannot control these factors, particularly in a person with naturally high arches, and even feet characterized by flattened arches will tend to roll over conventional arch support wedges. Moreover, arch support wedges require shoes and thus are impractical for certain athletes such as dancers.
Another approach to the problem has been to carefully wrap adhesive tape circularly around the arch and to connect it with tape extending rearwardly along each side of the foot and around the heel. The tape extending around the heel serves to maintain the circular portion in position and to act as a lateral restraint on foot motion thereby preventing excessive pronation. A further and highly significant advantage of tape over arch support and orthotics is in its ability to apply forces of the major foot joints against each other, providing a holding effect or enhanced retrograde stability unobtainable with any device that fits under the foot. To be effective, however, the tape must be applied very carefully in a prescribed manner by a qualified professional. Thus, this solution is not adapted for ordinary self-application. Also, tape has the disadvantage of stretching after a short time and any particular taping can last at most a few days. Further, the direction of pull and pressure cannot be adjusted after wrapping. In addition, tape does not assist in resupination of the foot. Tape also is irritating and cannot be used over.
Hence, those concerned with the development and use of orthopedic devices for the foot have long recognized the need for more effective devices, which are capable of self-application, for alleviating the problems caused by excessive pronation, and which will assist in resupination and provide enhanced retrograde stability approaching that of tape. A method and apparatus directed at these objectives is disclosed in the aforementioned U.S. Pat. No. 4,392,487. A sleeve and a connecting strap are wrapped around the foot in a prescribed fashion with the strap ends anchored to the sleeve. The sleeve is formed of a relatively elongate sheet of material and is elastic in the circumferential direction but is substantially inelastic in the lateral direction, with the opposite ends of the sheet adapted to be releasably joined together for adjustability. The strap is relatively narrow and elongate, and is formed of a material that is substantially inelastic in the longitudinal direction.
The sleeve is wrapped snugly around the arch of the foot with the ends of the sleeve joined together. The strap is wrapped from a location on the sleeve adjacent to the bottom of the foot, up across the instep, over the top of the foot and around the heel, from which position the strap is wrapped back to the sleeve and fastens thereto through an attachment loop near the instep. The strap is then tightened with the foot aligned in a preferred position (turned inwardly and rolled slightly medially upward). The substantial inelasticity of the strap and the fact that the sleeve is locked around the foot with both ends of the strap anchored to the sleeve on the medial side of the foot, all contribute to restraining the foot from excessive pronation and assisting in resupination during walking or running.
Use of such a foot stabilization apparatus has been found to be a generally effective solution. However, experience has taught that certain improvements in comfort, elasticity, restraint and holding effect are desirable. Among other things, for example, the anchor point of the releasably attachable end of the strap is fixed at a location rendering the strap substantially parallel to the forces exerted on the foot by walking or running and, therefore, the strap is not as efficient as it might be in restraining those forces and providing the desired holding effect. The substantial inelasticity of the sleeve in the lateral direction limits its ability to most comfortably conform to the shape of the foot. Further, adequate tightening of the inelastic strap to restrain excessive pronation can cause uncomfortable and unnecessary tension in the arch.
Accordingly, those concerned with the development and use of orthopedic devices for the foot have recognized the need for further improvement in the foregoing areas. The present invention fulfills the desire for these and other related improvements.